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ios - 如何从@objc函数在UIViewControllers之间传递数据数组

问题描述

我有一个孩子UICollectionViewController，我有一系列图像。当我删除任何照片时，我想将该更新图像数组发送回 Parent UIViewController。同样在子控制器中，我有一个编程view方式，当我单击任何图像以展开它时会调用它。当图像展开时，用户可以单击删除按钮从该阵列中删除照片。删除后我的数组已正确更新，但由于某些原因我无法将其发送回父级。我尝试使用代表和协议将其发回。这是我的子控制器代码：

protocol ListImagesDelegate {

    func receiveImagesUpdated(data: [String]?)
}

class ListImagesVC: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource {

// Properties
    var receivedImagesPath: [String]? = []
    var fullscreenImageView = UIImageView()
    var indexOfSelectedImage = 0
    var imagesAfterDelete: [String]? = []
    var delegate: ListImagesDefectDelegate?


override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)

        print("imagesAfterDelete: \(imagesAfterDelete ?? [])") // I'm getting the right number of images in this array.

        delegate?.receiveImagesUpdated(data: imagesAfterDelete)
    }


...
...

    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {

        print("Click on photo: \(indexPath.item + 1)")

        if let imagePath = receivedImagesPath?[indexPath.item] {

            guard let selectedImage = loadImageFromDiskWith(fileName: imagePath) else {return}

            setupFullscreenImageView(image: selectedImage)

            indexOfSelectedImage = indexPath.item
        }
    }

    private func setupFullscreenImageView(image: UIImage){

        fullscreenImageView = UIImageView(image: image)
        fullscreenImageView.frame = UIScreen.main.bounds
        fullscreenImageView.backgroundColor = .black
        fullscreenImageView.contentMode = .scaleAspectFit
        fullscreenImageView.isUserInteractionEnabled = true

        self.view.addSubview(fullscreenImageView)
        self.navigationController?.isNavigationBarHidden = true
        self.tabBarController?.tabBar.isHidden = true

        let deleteButton = UIButton(frame: CGRect(x: fullscreenImageView.bounds.maxX - 50, y: fullscreenImageView.bounds.maxY - 75, width: 30, height: 40))
        deleteButton.autoresizingMask = [.flexibleLeftMargin, .flexibleBottomMargin]
        deleteButton.backgroundColor = .black
        deleteButton.setImage(UIImage(named: "trashIcon"), for: .normal)
        deleteButton.addTarget(self, action: #selector(deleteButtonTapped), for: .touchUpInside)

        fullscreenImageView.addSubview(deleteButton)
    }

    @objc func deleteButtonTapped(button: UIButton!) {
        print("Delete button tapped")

        receivedImagesPath?.remove(at: indexOfSelectedImage)

        imagesAfterDelete = receivedImagesPath

        collectionView.reloadData()

        self.navigationController?.isNavigationBarHidden = false
        self.tabBarController?.tabBar.isHidden = false
        fullscreenImageView.removeFromSuperview()
    }

这是父控制器：


var updatedImages: [String]? = []

...
...

extension NewAlbumVC: ListImagesDelegate {

    func receiveImagesUpdated(data: [String]?) {

        print("New array: \(data ?? [])") // This print is never called.

        updatedImages = data

    }

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

        if segue.identifier == "goToImages" {

            let listImagesVC = segue.destination as! ListImagesVC

            listImagesVC.delegate = self
        }
    }
}

我想指定我的子控制器设置了 Storyboard ID ( "ListImagesID") 以及从父级到子级 ( "goToImages") 的 segue 标识符。会导致这任何冲突吗？

谢谢你读到这个。

标签： iosswift

解决方案

看来委托人来nil了

delegate?.receiveImagesUpdated(data: imagesAfterDelete)

为了这

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

要触发你必须有

self.performSegue(withIdentifier:"goToImages",sender:nil)

编辑：这个

let listImagesDefectVC = storyboard?.instantiateViewController(withIdentifier: "ListImagesDefectID") as!     ListImagesDefectVC
listImagesDefectVC.receivedImagesPath = imagesPath   
navigationController?.pushViewController(listImagesDefectVC, animated: true)

不会触发prepareForSegue，所以添加

listImagesDefectV.delegate = self

所以最后

解决方案 1：

@objc func tapOnImageView() { 
     let listImagesDefectVC = storyboard?.instantiateViewController(withIdentifier: "ListImagesDefectID") as! ListImagesDefectVC
     listImagesDefectVC.receivedImagesPath = imagesPath 
     listImagesDefectVC.delegate = self
     navigationController?.pushViewController(listImagesDefectVC, animated: true)
 }

解决方案 2： 

 @objc func tapOnImageView() {  
     self.performSegue(withIdentifier:"goToImages",sender:nil) 
 }

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

    if segue.identifier == "goToImages" {

        let listImagesVC = segue.destination as! ListImagesVC
        listImagesVC.receivedImagesPath = imagesPath 
        listImagesVC.delegate = self
    }
}

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